The present invention relates to apparatus for ascertaining the upper level of a supply of a flowable medium, e.g., a liquid, which is stored in a vessel, e.g., in an upright cylindrical tank. More particularly, the invention relates to improvements in apparatus of the type wherein files or rows of resistors and associated electric switches are mounted on an elongated insulating carrier which is adjacent to the path of upward or downward movement of a float. The float rides on the body of liquid in the vessel and carries a permanent magnet which actuates the nearest switch or switches to thereby change the number of resistors which are connected in circuit with an indicating instrument.
A somewhat similar apparatus is disclosed in U.S. Pat. No. 3,656,074 granted Apr. 11, 1972 to Bevilacqua et al. The patented apparatus employs an insulating carrier adapted to be flexed to the extent which is necessary to allow for its introduction into a slightly arcuate insulating pipe. The carrier cannot be folded or convoluted. Therefore, the manipulation of such apparatus presents serious problems when their components must be transported between different locales of use, especially if the length of the component parts must suffice to ascertain the upper level of liquid in a relatively large vessel, e.g., in a vessel wherein the upper level of liquid is located at several meters above the bottom wall. Similar problems arise when the apparatus must be removed from a vessel for the purpose of inspection and/or repair.
Attempts to assemble the insulating carrier for switches and resistors of several shorter sections which are coupled to each other at the locale of use, provided that the depth of the vessel warrants the use of two or more interconnected carrier sections, have met with negligible success because any shortening or lengthening of the carrier invariably entails a considerable amount of work which must be performed by skilled operators. Such work involves proper calibration of the indicating instrument whose pointer or another mobile part indicates or records the ascertained upper level of liquid in the vessel. Moreover, the resistance of connections between the conductors on discrete sections of the insulating carrier must be taken into consideration whenever the length of the carrier is increased or reduced.